Abstract: A heater for the rapid heating of water includes a main body having plural vertical upwardly opening chambers, combined with a molded cover plate that can be removably installed over the upper part of the main body. A plurality of combination heating and chamber partition assemblies extend downwardly from the bottom surface of the installed cover plate and one each of the assemblies resides in a main body chamber, each assembly including a generally flat and vertically elongated partition member and a pair of heating coils mounted to each partition member, one each coil on opposite sides of the partition member, and each partition member cooperates with a chamber to form a first channel for conducting water downwardly and a second channel for conducting water upwardly.